Yep i would make a formal complaint against the hospital if I was your SIL.
I had it in my birthplan that under no circumstances was my baby to be given formula unless it was at my request and by me.
My niece was born at a very bf- friendly hospital, but was rushed to Special Care because of breathing difficulties. Although the staff came around to collect colostrum from her, she later discovered that her bub was given formula first, without permission, for no apparent reason other than someone couldn't be bothered to walk down the corridor to see if she wanted to express or go to the nursery to feed.

So, yes, put it on your birthplan that no formula is to be given, but make sure that if you are separated from your baby (another issue in and of itself) your partner follows up with the staff looking after your bub who will probably not have read your birthplan.

C